Canola oil seed protein isolates having protein contents of at least 100 wt % (N×6.25) can be formed from oil seed meal by a process as described in copending U.S. patent application Ser. No. 10/137,391 filed May 3, 2002 (U.S. Patent Application Publication No. 2003-0125526 A1 and WO 02/089597) and U.S. patent application Ser. No. 10/476,230 filed Jun. 9, 2004 (U.S. Patent Application Publication No. 2004-0254353 A1), assigned to the assignee hereof and the disclosures of which are incorporated herein by reference. The procedure involves a multiple step process comprising extracting canola oil seed meal using an aqueous salt solution, separating the resulting aqueous protein solution from residual oil seed meal, increasing the protein concentration of the aqueous solution to at least about 200 g/L while maintaining the ionic strength substantially constant by using a selective membrane technique, diluting the resulting concentrated protein solution into chilled water to cause the formation of protein micelles, settling the protein micelles to form an amorphous, sticky, gelatinous, gluten-like protein micellar mass (PMM), and recovering the protein micellar mass from supernatant having a protein content of at least about 100 wt % (N×6.25). As used herein, protein content is determined on a dry weight basis. The recovered PMM may be dried.
In one embodiment of the process, the supernatant from the PMM settling step is processed to recover canola protein isolate from the supernatant. This procedure may be effected by initially concentrating the supernatant using an ultrafiltration membrane and drying the concentrate. The resulting canola protein isolate has a protein content of at least about 90 wt %, preferably at least about 100 wt % (N×6.25).
The procedures described in U.S. patent application Ser. No. 10/137,391 are essentially batch procedures. In copending U.S. patent application Ser. No. 10/298,678 filed Nov. 19, 2002 (U.S. Patent Application Publication No. 2004-0039174 A1 and WO 03/043439) and U.S. patent application Ser. No. 10/496,071 filed Mar. 5, 2005 (U.S. Patent Application Publication No. 2003-0015910 A1), assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, there is described a continuous process for making canola protein isolates. In accordance therewith, canola oil seed meal is continuously mixed with an aqueous salt solution, the mixture is conveyed through a pipe while extracting protein from the canola oil seed meal to form an aqueous protein solution, the aqueous protein solution is continuously conveyed through a selective membrane operation to increase the protein content of the aqueous protein solution to at least about 50 g/L, while maintaining the ionic strength substantially constant, the resulting concentrated protein solution is continuously mixed with chilled water to cause the formation of protein micelles, and the protein micelles are continuously permitted to settle while the supernatant is continuously overflowed until the desired amount of PMM has accumulated in the settling vessel. The PMM is recovered from the settling vessel and may be dried. The PMM has a protein content of at least about 90 wt % (N×6.25), preferably at least about 100 wt %. The overflowed supernatant may be processed to recover canola protein isolate therefrom, as described above.
Canola seed is known to contain about 10 to about 30 wt % proteins and several different protein components have been identified. These proteins include a 12S globulin, known as cruciferin, a 7S protein and a 2S storage protein, known as napin. As described in copending U.S. patent application Ser. No. 10/413,371 filed Apr. 15, 2003 (U.S. Patent Application Publication No. 2004-0034200 A1 and WO 03/088760) and U.S. patent application Ser. No. 10/510,766 filed Apr. 29, 2005 (U.S. Patent Application Publication No. 2005-0249828 A1), assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, the procedures described above, involving dilution of concentrated aqueous protein solution to form PMM and processing of supernatant to recover additional protein, lead to the recovery of isolates of different protein profiles.
In this regard, the PMM-derived canola protein isolate has a protein component composition of about 60 to about 98 wt % of 7S protein, about 1 to about 15 wt % of 12S protein and 0 to about 25 wt % of 2S protein. The supernatant-derived canola protein isolate has a protein component composition of about 60 to about 95 wt % of 2S protein, about 5 to about 40 wt % of 7S protein and 0 to about 5 wt % of 12S protein. Thus, the PMM-derived canola protein isolate is predominantly 7S protein and the supernatant-derived canola protein isolate is predominantly 2S protein. As described in the aforementioned U.S. patent application Ser. No. 10/413,371, the 2S protein has a molecular mass of about 14,000 daltons, the 7S protein has a molecular mass of about 145,000 daltons and the 12S protein has a molecular mass of about 290,000 daltons.
In copending U.S. patent application Ser. No. 11/038,086 filed Jan. 21, 2005 (U.S. Patent Publication No. 2005-0181112 A1 and WO 2005/067729) and Ser. No. 12/213,500 filed Jun. 20, 2008 assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, there is described a procedure wherein the supernatant is heat-treated to deposit 7S protein and provide an aqueous protein solution enriched in 2S protein. This aqueous protein solution may be dried to provide a 2S-enriched canola protein isolate. This canola protein isolate has many benefits, including solubility over a wide range of acid pH values and clarity in aqueous medium, making it possible, for example, to prepare protein fortified beverages, particularly at acid pH values, in which the clarity is not impaired by the addition of the canola protein isolate.
Canola is also known as rapeseed or oil seed rape.